High-speed data rates common in networking environments, such as 100 gigabits-per-second (Gb/s), require multiplexers to create a serial stream from several lower-rate signals. At a 50 GHz operating frequency, for example, 2:1 and 4:1 multiplexers are known in the art. Such devices are configured with two or four inputs and a single, multiplexed output. Currently, 5:1 multiplexers are not available for high-speed applications, such as 50 GHz.
100 Gigabit Ethernet (100 GbE) is an Ethernet standard presently under early development by the Institute of Electrical and Electronics Engineers (IEEE). In late November of 2006, an IEEE study group agreed to target 100 GbE as the next version of the technology. Additionally, high-speed optical systems are moving beyond the existing 10 Gb/s line rates to higher time-division-multiplexed (TDM) rates, such as 40 Gb/s and 100 Gb/s. Advantageously, 100 Gb/s optical signals offer an effective way to achieve 1 Tb/s utilizing 10 wavelengths of 100 Gb/s signals over wavelength division multiplexing.
Disadvantageously, the lack of 5:1 multiplexers will require multiple cascaded multiplexers with several clocks to achieve a native 100 GbE or 100 Gb/s signal. Alternatively, 100 GbE could be transmitted in parallel, such as five 20 Gb/s signals. However, this solution is inefficient with respect to the transmission rate, requiring five transmitters and receivers per signal. A 100 Gb/s signal for optical transmission would not be transmitted in parallel because this would remove any advantage of having a higher TDM rate.
A 5:1 multiplexer could be formed using 4:1 and 2:1 multiplexers; however such an implementation requires three bit clock control which requires gating of three clocks. Disadvantageously, this gating is a very challenging approach. Additionally, existing 4:1 multiplexers at high data rates (e.g., 50 Gb/s and the like) utilize clock division internally, and therefore cannot be used in combination with a 2:1 multiplexer to create a 5:1 multiplexer.
No known native 5:1 multiplexers exist for high data rates, such as 50 Gb/s or 100 Gb/s. Thus, there exists a need for a 5:1 multiplexer operable at high data rates with a single reference clock.